#include <windows.h>
#include <windowsx.h>

#define ID_TIMER    1
#define STRMAXLEN  25 //一个显示列的最大长度
#define STRMINLEN  8  //一个显示列的最小长度

LRESULT CALLBACK WndProc (HWND, UINT, WPARAM, LPARAM) ;
//////////////////////////////////////////////////////////////////
//////////////////////////////////////////////////////////////////
typedef struct tagCharChain //整个当作屏幕的一个显示列,这是个双向列表
{
        struct tagCharChain *prev; //链表的前个元素
        TCHAR  ch;                  //一个显示列中的一个字符
        struct tagCharChain *next; //链表的后个元素
}CharChain, *pCharChain;

typedef struct tagCharColumn
{
        CharChain *head, *current, *point;
        int x, y, iStrLen; //显示列的开始显示的x,y坐标,iStrLen是这个列的长度
        int iStopTimes, iMustStopTimes; //已经停滞的次数和必须停滞的次数,必须停滞的次数是随机的
}CharColumn, *pCharColumn;

int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance,
                    PSTR szCmdLine, int iCmdShow)
{
        static TCHAR szAppName[] = TEXT ("matrix") ;
        HWND            hwnd ;
        MSG            msg ;
        WNDCLASS    wndclass ;

        wndclass.style                = CS_HREDRAW | CS_VREDRAW ;
        wndclass.lpfnWndProc        = WndProc ;
        wndclass.cbClsExtra        = 0 ;
        wndclass.cbWndExtra        = 0 ;
        wndclass.hInstance        = hInstance ;
        wndclass.hIcon                = LoadIcon (NULL, IDI_APPLICATION) ;
        wndclass.hCursor        = LoadCursor (NULL, IDC_ARROW) ;
        wndclass.hbrBackground        = (HBRUSH) GetStockObject (BLACK_BRUSH) ;
        wndclass.lpszMenuName        = NULL ;
        wndclass.lpszClassName        = szAppName ;

        if(!RegisterClass (&wndclass))
        {
            MessageBox (NULL, TEXT ("此程序必须运行在NT下!"), szAppName, MB_ICONERROR) ;
            return 0;
        }

        hwnd = CreateWindow (szAppName, NULL,
                            WS_DLGFRAME | WS_THICKFRAME | WS_POPUP,
                            0, 0,
                            GetSystemMetrics(SM_CXSCREEN), GetSystemMetrics(SM_CYSCREEN),
                            NULL, NULL, hInstance,
                            NULL) ;

        ShowWindow (hwnd, SW_SHOWMAXIMIZED) ; //最大化显示
        UpdateWindow (hwnd) ;
        ShowCursor(FALSE); //隐藏鼠标光标
        
        srand ((int) GetCurrentTime ()) ; //初始化随机数发生器
        while (GetMessage (&msg, NULL, 0, 0))
        {
            TranslateMessage (&msg) ;
            DispatchMessage (&msg) ;
        }
        ShowCursor(TRUE); //显示鼠标光标
        return msg.wParam ;
}

TCHAR randomChar() //随机字符产生函数
{
        return (TCHAR)(rand()%(126-33)+33); //33到126之间
}

int init(CharColumn *cc, int cyScreen, int x) //初始化
{
        int j;
        cc->iStrLen = rand()%(STRMAXLEN-STRMINLEN) + STRMINLEN; //显示列的长度
        cc->x = x+3 ;        //显示列的开始显示的x坐标
        cc->y =rand()%3?rand()%cyScreen:0; //显示列的开始显示的y坐标
        cc->iMustStopTimes = rand()%6 ;
        cc->iStopTimes    = 0 ;
        cc->head = cc->current =
                        (pCharChain)calloc(cc->iStrLen, sizeof(CharChain)); //生成显示列
        for(j=0; j<cc->iStrLen-1; j++)
        {
                cc->current->prev = cc->point; //cc->point一个显示列的前个元素
                cc->current->ch  = '\0';
                cc->current->next = cc->current+1; //cc->current+1一个显示列的后个元素
                cc->point          = cc->current++; //cc->point = cc->current; cc->current++;
        }
        cc->current->prev = cc->point; //最后一个节点
        cc->current->ch  = '\0';
        cc->current->next = cc->head;
        cc->head->prev    = cc->current; //头节点的前一个为此链的最后一个元素

        cc->current = cc->point = cc->head; //free掉申请的内存要用current当参数
        cc->head->ch = randomChar(); // 对链表头的 元素填充
        return 0;
}

LRESULT CALLBACK WndProc (HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)
{
      HDC          hdc ;
      //ctn 用来确定一个显示链是否 向下前进,如果等待次数超过必须等待的次数,ctn就代表要向下前进
      int i, j, temp, ctn; //j为一个显示链中除链表头外的在屏幕上显示的y坐标,temp绿色过度到黑色之用
      static  HDC hdcMem;
      HFONT    hFont;
      static  HBITMAP hBitmap;
      static  int cxScreen, cyScreen; //屏幕的宽度 高度.
      static  int iFontWidth=10, iFontHeight=15, iColumnCount; //字体的宽度 高度, 列数
      static  CharColumn *ccChain;

      switch (message)
      {
        case WM_CREATE:
            cxScreen = GetSystemMetrics(SM_CXSCREEN) ; //屏幕宽度
            cyScreen = GetSystemMetrics(SM_CYSCREEN) ;
            SetTimer (hwnd, ID_TIMER, 10, NULL) ;

            hdc = GetDC(hwnd);
            hdcMem = CreateCompatibleDC(hdc);
            hBitmap = CreateCompatibleBitmap(hdc, cxScreen, cyScreen);
            SelectObject(hdcMem, hBitmap);
            ReleaseDC(hwnd, hdc);
            //创建字体
            hFont = CreateFont(iFontHeight, iFontWidth-5, 0, 0, FW_BOLD, 0, 0, 0,
                                DEFAULT_CHARSET, OUT_DEFAULT_PRECIS, CLIP_DEFAULT_PRECIS,
                                DRAFT_QUALITY, FIXED_PITCH | FF_SWISS, TEXT("Fixedsys"));
            SelectObject(hdcMem, hFont);
            DeleteObject (hFont) ;
            SetBkMode(hdcMem, TRANSPARENT); //设置背景模式为 透明
            iColumnCount = cxScreen/(iFontWidth*3/2); //屏幕所显示字母雨的列数

            ccChain = (pCharColumn)calloc(iColumnCount, sizeof(CharColumn));
            for(i=0; i<iColumnCount; i++)
            {
                init(ccChain+i, cyScreen, (iFontWidth*3/2)*i);
            }
            return 0 ;

        case WM_TIMER:
            hdc = GetDC(hwnd);
            PatBlt (hdcMem, 0, 0, cxScreen, cyScreen, BLACKNESS) ; //将内存设备映像刷成黑色
            for(i=0; i<iColumnCount; i++)
            {
                ctn = (ccChain+i)->iStopTimes++ > (ccChain+i)->iMustStopTimes;
                //
                (ccChain+i)->point = (ccChain+i)->head; //point用于遍历整个显示列
                
                //第一个字符显示为 白色
                SetTextColor(hdcMem, RGB(255, 255, 255));
                TextOut(hdcMem, (ccChain+i)->x, (ccChain+i)->y, &((ccChain+i)->point->ch), 1);
                j = (ccChain+i)->y; 
                (ccChain+i)->point = (ccChain+i)->point->next;
                //遍历整个显示列,将这个显示列里的字符从下往上显示
                temp = 0 ; //temp绿色过度到黑色之用
                while((ccChain+i)->point != (ccChain+i)->head && (ccChain+i)->point->ch)
                {
                        SetTextColor(hdcMem, RGB(0, 255-(255*(temp++)/(ccChain+i)->iStrLen), 0));
                        TextOut(hdcMem, (ccChain+i)->x, j-=iFontHeight, &((ccChain+i)->point->ch), 1);
                        (ccChain+i)->point = (ccChain+i)->point->next;
                }
                if(ctn)
                    (ccChain+i)->iStopTimes = 0 ;
                else continue;
                (ccChain+i)->y += iFontHeight; //下次开始显示的y坐标 为当前的y坐标加上 一个字符的高度
                //如果开始显示的y坐标减去 整个显示列的长度超过了屏幕的高度
                if( (ccChain+i)->y-(ccChain+i)->iStrLen*iFontHeight > cyScreen)
                {
                        free( (ccChain+i)->current );
                        init(ccChain+i, cyScreen, (iFontWidth*3/2)*i);
                }
                //链表的头 为此链表的前个元素,因为下次开始显示的时候 就相当与在整个显示列的开头添加个元素,然后在开始往上显示
                (ccChain+i)->head = (ccChain+i)->head->prev;
                (ccChain+i)->head->ch = randomChar();
            }
            
            BitBlt(hdc, 0, 0, cxScreen, cyScreen, hdcMem, 0, 0, SRCCOPY);
            ReleaseDC(hwnd, hdc);
            return 0;

        case WM_RBUTTONDOWN:
            KillTimer (hwnd, ID_TIMER) ;
            return 0;

        case WM_RBUTTONUP:
            SetTimer (hwnd, ID_TIMER, 10, NULL) ;
            return 0;

        //处理善后工作
        case WM_KEYDOWN:
        case WM_LBUTTONDOWN:
        case WM_DESTROY:
            KillTimer (hwnd, ID_TIMER) ;
            DeleteObject(hBitmap);
            DeleteDC(hdcMem);
            for(i=0; i<iColumnCount; i++)
            {
                free( (ccChain+i)->current );
            }
            free(ccChain);
            PostQuitMessage (0) ;
            return 0 ;
        }
        return DefWindowProc (hwnd, message, wParam, lParam) ;
}


